Apparatus and method for displaying holographic three-dimensional image

ABSTRACT

An apparatus for displaying a holographic three-dimensional (3D) image is provided. The apparatus includes: a holographic pattern generation unit; a spatial optical modulation device including a phase transition layer formed of a phase transition material, a phase of which is changed by a temperature. A holographic pattern generated by the holographic pattern generation unit is optically addressed on the spatial optical modulation device. The apparatus also includes a heat source for applying heat to the phase transition layer; a control unit for controlling the heat source according to holographic pattern information generated by the holographic pattern generation unit; and a reproduction light source for irradiating light for image reproduction onto the spatial optical modulation device.

RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.10-2013-0152609, filed on Dec. 9, 2013, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND

1. Field

Apparatuses and methods consistent with exemplary embodiments relate todisplaying a holographic three-dimensional (3D) image.

2. Description of the Related Art

Along with the increase in demand for 3D image display apparatuses,research for a spatial optical modulator which may be employed inapparatuses for displaying a holographic 3D image has been conducted.

Compared to a method of using a binocular parallax, a method ofgenerating a 3D image using the principle of holography causes littleeye strain and forms a very natural stereoscopic image.

To obtain a desired image in a typical holography method, aninterference pattern is obtained by irradiating an object with two ormore light beams, e.g., a reference beam and a writing beam, and ahologram pattern is formed by projecting the interference pattern onto amaterial having a refractive index which varies with light. Thereafter,a stereoscopic image of the object is reproduced by irradiating thereference beam onto the hologram pattern. However, although this methodmay be used to obtain a single image, it is difficult to use this methodto realize various images or a video.

Recently, to form a hologram pattern, methods capable of generating apattern corresponding to a 3D image using a virtual method throughcomputation using a computer have been proposed instead of a methoddirectly using existing light interference. Along with the improvementin computer performance, the possibility of realizing a 3D video byusing a computer generated hologram has gradually increased, andaccordingly, an optical modulation device capable of reversiblywriting/reproducing a generated hologram pattern is desired.

SUMMARY

One or more exemplary embodiments may provide apparatuses and methodsfor displaying a holographic three-dimensional (3D) image.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

According to an aspect of an exemplary embodiment, an apparatus fordisplaying a holographic three-dimensional (3D) image includes: aholographic pattern generation unit which generates holographic patterninformation; a spatial optical modulation device on which a holographicpattern generated by the holographic pattern generation unit is to beoptically addressed, the spatial optical modulation device including aphase transition layer formed of a phase transition material, a phase ofwhich changes according to a temperature; a heat source which appliesheat to the phase transition layer; a control unit which controls theheat source according to the holographic pattern information; and areproduction light source which irradiates light for image reproductiononto the spatial optical modulation device.

The heat source may be a laser light source.

The phase transition material may be a material that undergoes a Motttransition.

The phase transition material may include a material selected from agroup consisting of vanadium dioxide (VO₂), vanadium trioxide (V₂O₃),europium oxide (EuO), manganese oxide (MnO), cobalt oxide (CoO), cobaltdioxide (CoO₂), lithium cobalt dioxide (LiCoO₂, calcium ruthenium oxide(Ca₂RuO₄), strontium lawrencium oxide (SrLrO₄), and copper chloride(CuCl).

The spatial optical modulation device may further include a firstsubstrate on which the phase transition layer is formed.

The phase transition layer may be patterned onto a plurality of regionsthat are separated from one other.

Spaces between the plurality of regions may be vacuum-sealed.

A second substrate may be formed on the phase transition layer, and asealing member for vacuum-sealing the space between the plurality ofregions may be formed between the first substrate and the secondsubstrate.

The first substrate on which the phase transition layer patterned ontothe plurality of regions is formed may be arranged in a vacuumstructure.

An optical absorption layer may be formed between the first substrateand the phase transition layer.

The optical absorption layer may be formed of a black polymer and aplurality of metal nanostructures dispersed throughout the blackpolymer.

The metal nanostructures each may have a spherical nanoparticle shape.

A diameter of the spherical nanoparticle shape may be the same as athickness of the optical absorption layer.

The metal nanostructures each may have a nanorod or nanowire shape.

The metal nanostructures each may have a length that is equal to adistance between the first substrate and the phase transition layer, anda longitudinal direction of the nanorod may be arranged in a directionoriented toward the phase transition layer.

A reflective layer may be formed between the first substrate and thephase transition layer.

A reflective layer may be formed between the optical absorption layerand the phase transition layer.

The spatial optical modulation device may further include a liquidcrystal layer.

The spatial optical modulation device may include: the first substrate;a first electrode layer formed on the first substrate; the phasetransition layer formed on the first electrode layer; the liquid crystallayer formed on the phase transition layer; a second electrode layerformed on the liquid crystal layer; and the second substrate formed onthe second electrode layer.

The phase transition layer may be patterned onto a plurality of regionsthat are separated from one other.

The apparatus may further include a sensor for measuring an ambienttemperature of the phase transition layer.

The control unit may store therein a cooling curve function of the phasetransition material forming the phase transition layer and adjust theintensity of the heat source according to the ambient temperaturemeasured by the sensor.

According to an aspect of another exemplary embodiment, a method ofdisplaying a holographic three-dimensional (3D) image includes: applyingheat to a spatial optical modulation device having a phase transitionlayer formed of a phase transition material, according to holographicpattern information, so that the phase transition layer is heated to aphase transition temperature or more; and irradiating reproduction lighton the spatial optical modulation device.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other exemplary aspects and advantages will become apparentand more readily appreciated from the following description of theembodiments, taken in conjunction with the accompanying drawings inwhich:

FIGS. 1A and 1B are block diagrams of an apparatus for displaying aholographic three-dimensional (3D) image, respectively showing a statein which phase transition does not occur in a phase transition layer anda state in which phase transition occurs in the phase transition layerto thereby form a holographic pattern, according to an exemplaryembodiment;

FIG. 2 is a flowchart of a method of displaying a holographic 3D image,according to an exemplary embodiment;

FIGS. 3 to 10 illustrate various structures of a spatial opticalmodulation device which may be employed in the apparatus of FIGS. 1A and1B, according to exemplary embodiments:

FIGS. 11A and 11B are block diagrams of an apparatus for displaying aholographic 3D image, respectively showing a state in which phasetransition does not occur in a phase transition layer and a state inwhich phase transition occurs in the phase transition layer to therebyform a holographic pattern on a liquid crystal layer, according toanother exemplary embodiment; and

FIG. 12 illustrates a spatial optical modulation device which may beemployed in the apparatus of FIGS. 11A and 11B, according to anotherexemplary embodiment.

DETAILED DESCRIPTION

Exemplary embodiments are illustrated in the drawings and described indetail herein. The exemplary embodiments may allow various kinds ofchange or modification and various changes in form. Advantages andfeatures of the embodiments and a method for achieving them will beclear with reference to the accompanying drawings. The exemplaryembodiments may be embodied in many different forms and should not beconstrued as being limited to the descriptions set forth herein.

Reference will now be made in detail to exemplary which are illustratedin the accompanying drawings, wherein like reference numerals refer tolike elements throughout. In this regard, the present embodiments mayhave different forms and should not be construed as being limited to thedescriptions set forth herein. Accordingly, the embodiments are merelydescribed below, by referring to the figures, to explain aspects of thepresent description.

It will be understood that although the terms “first”, “second”, etc.may be used herein to describe various components, these componentsshould not be limited by these terms. These components are only used todistinguish one component from another.

As used herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise.

It will be further understood that the terms “comprises” and/or“comprising” used herein specify the presence of stated features orcomponents, but do not preclude the presence or addition of one or moreother features or components.

It will be understood that when a layer, region, or component isreferred to as being “formed on,” another layer, region, or component,it can be directly or indirectly formed on the other layer, region, orcomponent. That is, for example, intervening layers, regions, orcomponents may be present.

Sizes of elements in the drawings may be exaggerated for convenience ofexplanation. In other words, since sizes and thicknesses of componentsin the drawings are arbitrarily illustrated for convenience ofexplanation, the following embodiments are not limited thereto.

As used herein, the term “and/or” includes any and all combinations ofone or more of the associated listed items.

FIGS. 1A and 1B are block diagrams of an apparatus 500 for displaying aholographic 3D image, respectively showing a state in which phasetransition does not occur in a phase transition layer 220 and a state inwhich phase transition occurs in the phase transition layer 220 tothereby form a holographic pattern P, according to an exemplaryembodiment.

The apparatus 500 includes a holographic pattern generation unit 110, aspatial optical modulation device 200 which includes the phasetransition layer 220 formed of a phase transition material of which aphase changes according to temperature and which optically addresses theholographic pattern P generated by the holographic pattern generationunit 110, a heat source 120 for applying heat to the phase transitionlayer 220, a control unit 130 for controlling the heat source 120according to holographic pattern information generated by theholographic pattern generation unit 110, and a reproduction light sourceunit 190 for irradiating light for image reproduction to the spatialoptical modulation device 200. The holographic pattern generation unit110, the control unit 130, and the reproduction light source unit mayeach comprise one or more computer processors or other computercircuitry.

The holographic pattern generation unit 110 generates the holographicpattern P containing the 3D image information using a virtual method. Inother words, a detailed form of an interference pattern which may beobtained by irradiating a reference beam and a writing beam onto anobject is calculated by a computer simulation. As the performance of acomputer increases, a holographic pattern containing various pieces ofimage or video information may be formed.

The spatial optical modulation device 200 is provided to reversiblyrecord or reproduce the holographic pattern P formed by the holographicpattern generation unit 110. The spatial optical modulation device 200employs a phase transition material in which a phase transition occursbased on a temperature and may have, for example, a structure in whichthe phase transition layer 220 is formed on a first substrate 210.

The first substrate 210 is a base for forming the phase transition layer220, and a substrate of any of various materials may be used for thefirst substrate 210. For example, the first substrate 210 may be formedof a light-transmissive material or a material having a high heatconductivity by which heat may be easily transferred to the phasetransition layer 220.

The phase transition layer 220 may be formed of a material in which aphase transition occurs based on a temperature. The material is amaterial that undergoes a Mott transition, in which an electricalcharacteristic of the material changes by phase transition, such asinsulator-metal transition, semiconductor-metal transition,semiconductor-insulator transition, or the like, or a magneticcharacteristic of the material changes by phase transition, such asmagnetic-nonmagnetic transition or the like. The material may correspondto, for example, vanadium dioxide (VO₂), vanadium trioxide (V₂O₃),titanium (Ti)-doped VO₂, Ti-doped V₂O₃, europium oxide (EuO), manganeseoxide (MnO), cobalt oxide (CoO), cobalt dioxide (CoO₂), lithium cobaltdioxide (LiCoO₂), calcium ruthenium oxide (Ca₂RuO₄), strontium(Sr)-doped Ca₂RuO₄, strontium lawrencium oxide (SrLrO₄), copper chloride(CuCl), or the like. When a temperature that is a phase transitiontemperature or greater is induced in a particular location of thematerial, a material characteristic at the location may vary, and thus,an optical characteristic of the material may vary, thereby forming theholographic pattern P on the phase transition layer 220.

In order to realize a video with holographic 3D images, a writing timeis also important, and since a phase transition time of Mott transitionis in the picoseconds to femtoseconds, a writing time is very short evenfor gigabytes of data. In addition, high resolution holographic 3Dimages may be realized using the phase transition material. When phasetransition occurs based on a temperature, since a variation width of thephase transition occurring at a temperature that is equal to or higherthan the phase transition temperature is very narrow, even though thewriting beam, that is, a beam irradiated by the heat source 120 to heatthe phase transition layer 220, has a Gaussian distribution, highresolution holographic 3D images may be realized. Accordingly, a minutepattern that is less than a beam spot size may be formed on the phasetransition layer 220 by adjusting the thermal energy of the beam that isirradiated onto the phase transition layer 220.

The heat source 120 may apply heat so as to form the holographic patternP on the phase transition layer 220. For the heat source 120, a laserlight source may be used, and the laser light source irradiates laserbeams on the phase transition layer 220 so that the temperature of aparticular location of the phase transition layer 220 is raised to aparticular temperature, thereby forming the holographic pattern Pgenerated by the holographic pattern generation unit 110. The phasetransition layer 220 is heated with a preset heat intensity distributionso as to form a pattern corresponding to a 3D image at every localregion of the phase transition layer 220. To this end, the laser lightsource used for the heat source 120 may be configured so that theintensity and direction of the laser light can scan the phase transitionlayer 220 under control of the control unit 130. Alternatively, an arrayof a plurality of laser light sources may be used so that a desiredtemperature distribution for forming the holographic pattern P isobtained quickly on the whole area of the phase transition layer 220.

The reproduction light source unit 190 may reproduce a 3D imagecontained in the holographic pattern P formed on the phase transitionlayer 220. The reproduction light source unit 190 is provided toirradiate, as reproduction light Lr, light having the same properties,e.g., the same wavelength and phase, as the reference beam used in thecomputer simulation for generating the holographic pattern P by usingthe holographic pattern generation unit 110. The reproduction lightsource unit 190 may have a configuration capable of quickly scanning thespatial optical modulation device 200 or may be formed having a surfacelight source device so that the reproduction light Lr can be irradiatedsimultaneously onto the whole area of the spatial optical modulationdevice 200.

The apparatus 500 may further include a sensor 140 for measuring anambient temperature of the phase transition layer 220. A cooling speedof the phase transition layer 220 is associated with the ambienttemperature. For example, the apparatus 500 may store therein a coolingcurve function of the phase transition material forming the phasetransition layer 220 and adjust the intensity of the heat source 120 inconsideration of the temperature measured by the sensor 140.

FIG. 2 is a flowchart of a method of displaying a holographic 3D image,according to an embodiment of the present invention.

The method includes applying heat to a spatial optical modulation devicehaving a phase transition layer formed of a phase transition material,according to holographic pattern information, so that the phasetransition layer is heated to a phase transition temperature or more andirradiating reproduction light on the spatial optical modulation device.

The apparatus 500 shown in FIGS. 1A and 1B is an illustrative structurefor implementing the method, and the method will now be described indetail with reference to FIGS. 1A and 1B.

The holographic pattern generation unit 110 forms a holographic patterncorresponding to a 3D image to be displayed. For example, a hologrampattern corresponding to a 3D image having a plurality of frames N isgenerated in operation S1. In detail, a frame rate FR expressed as anumber of frames per second for displaying a video and a total number Nof frames are determined in operation S1. Operation S1 is performedthrough a computer simulation, and a calculation result is stored.

The control unit 130 determines a temperature distribution of the phasetransition layer 220 that is necessary for forming each frame image andcontrols the heat source 120 on the basis of the determined temperaturedistribution. For example, the temperature distribution of the phasetransition layer 220 is determined from the frame rate FR, an ambienttemperature, and a cooling curve function of a phase transition materialforming the phase transition layer 220 in operation S2.

For example, when the phase transition temperature is 70° C., and thecooling curve function of the phase transition material has a coolingspeed of 1° C./msec, heat is applied to the phase transition layer 220so that the temperature of the phase transition material cools to 101°C., which is 31° C. higher than the phase transition temperature. Inthis case, the temperature of the phase transition material becomes 69°C. after 32 msec have elapsed following phase transition, and thus, oncethe temperature of the phase transition material has cooled to 69° C.,the phase transition material returns to an original phase. That is,since a holographic pattern corresponding to a corresponding image ismaintained only for 32 msec, an operation of about 30 Hz may beperformed.

When a holographic pattern is generated, after the frame rate FR isdetermined, an ambient temperature is measured, and a coolingtemperature per second starting from the measured ambient temperature isderived from the cooling curve function of the phase transitionmaterial. Accordingly, a temperature T of the phase transition layer 220may be defined as below.

T=(phase transition temperature)+(1/FR)*(cooling temperature persecond).

In this manner, when a temperature which is desired for an area formedof all local regions in the phase transition layer 220, i.e., atemperature distribution, is determined, heat is applied to the phasetransition layer 220 on the basis of the temperature distribution inoperation S3.

The calculation method described above is illustrative, and variousfactors for more accurate calculation may be stored in the control unit130 together with the cooling curve function of the phase transitionmaterial, and a temperature distribution to be formed in the phasetransition layer 220 may be calculated using the various factors and thecooling curve function of the phase transition material.

A laser light source used for the heat source 120 irradiates a writingbeam Lw, which is light for heating the phase transition layer 220,thereby forming a corresponding holographic pattern P on the phasetransition layer 220. The reproduction light source unit 190 irradiatesreproduction light Lr on the spatial optical modulation device 200 inoperation S4, and a 3D image is reproduced due to interference betweenthe reproduction light Lr and the holographic pattern P.

As described above, the temperature distribution of the phase transitionlayer 220 is set to become lower than the phase transition temperaturewhen a time corresponding to inverse of the frame rate, 1/FR elapses.Therefore, the holographic pattern P formed on the phase transitionlayer 220 disappears when an elapsed timed after laser light irradiationis greater than 1/FR since the temperature of the phase transition layer220 is lower than the phase transition temperature and the phasetransition material of the phase transition layer 220 returns to anoriginal phase. Accordingly, a holographic pattern corresponding to anext frame image may be formed.

In order to form the holographic pattern corresponding to the next frameimage, a temperature distribution of the phase transition layer 220corresponding to the holographic pattern containing the next frame imageis determined in operation S2, and heat is applied to the phasetransition layer 220 according to the temperature distribution of thephase transition layer 220 in operation S3. A temperature distributionof the phase transition layer 220 for forming holographic patternscorresponding to a plurality of frame images may be calculated andstored in operation S1, in advance of generating the hologram patterncorresponding to the 3D image corresponding to the plurality of frames,and the heat source 120 may be controlled according to the temperaturedistribution of the phase transition layer 220 in operation S3 byapplying heat to the phase transition layer 220.

FIGS. 3 to 10 illustrate various structures of a spatial opticalmodulation device which may be employed in the apparatus 500 of FIG. 1,according to exemplary embodiments.

FIGS. 3 to 5 illustrate structures that are relatively effective forobtaining a minute pattern so as to increase resolution.

Referring to FIG. 3, a spatial optical modulation device 201 includesthe first substrate 210 and a phase transition layer 221 formed on thefirst substrate 210. The phase transition layer 221 is patterned onto aplurality of regions 222 that are separated from each other.

The phase transition layer 221 may be formed by depositing a phasetransition material to form a thin-film form as shown in FIG. 1A andusing an etching process. Alternatively, the phase transition layer 221may be formed using a nanowire growth method involving a vertical growthmethod. The diameter of each region 222 may be on the order of hundredsnanometers or less. In addition, a gap between the regions 222 may be onthe order of several nanometers to hundreds of nanometers.

The structure of the phase transition layer 221 as illustrated in FIG. 3may be used to form a relatively accurate holographic pattern byreducing an influence from adjacent regions when local regions of thephase transition layer 221 are heated with different intensities ofheat. Since the structure has poor heat transfer between adjacentregions 222 due to an air layer between the adjacent regions 222, whenthe writing beam Lw irradiated by the heat source 120 is irradiated ontoa particular part of the phase transition layer 221, heat may beprevented from spreading along the phase transition layer 221 andwidening a pattern.

Referring to FIG. 4, a spatial optical modulation device 202 includesthe first substrate 210, the phase transition layer 221 patterned ontothe plurality of regions 222, a second substrate 240 on the phasetransition layer 221, and a sealing member 230 formed between the firstsubstrate 210 and the second substrate 240 around the regions of thephase transition layer.

The structure of the phase transition layer 221 as illustrated in FIG. 4may increase an insulation effect between the plurality of regions 222by vacuum-sealing a space between the plurality of regions 222. Sinceheat transfer between adjacent regions is blocked in a vacuum state,when local regions of the phase transition layer 221 are heated withdifferent intensities of heat, adjacent regions may be further preventedfrom influencing one another.

Referring to FIG. 5, a spatial optical modulation device 203 includesthe first substrate 210 on which the phase transition layer 221patterned onto the plurality of regions 222 is formed, and which isarranged in a vacuum structure 300. The vacuum structure 300 may beformed with two substrates 310 and 330 separated from each other and asealing member 320 surrounding the periphery between the two substrates310 and 330. However, the spatial optical modulation device 203 is notlimited to the structure shown in FIG. 5, and the vacuum structure 300may be modified to various forms of structures capable of forming avacuum therein.

FIGS. 6 to 9 illustrate spatial optical modulation devices 204, 205,207, and 208 employing an optical absorption layer together with thephase transition layer 220, respectively.

Referring to FIG. 6, the spatial optical modulation device 204 includesthe first substrate 210, an optical absorption layer 250, and the phasetransition layer 220. The optical absorption layer 250 may block thewriting beam Lw from the heat source 120, such as a laser light source,from being transferred to a viewer. Although the optical absorptionlayer 250 is present, the writing beam Lw from the heat source 120should be able to heat the phase transition layer 220. For the opticalabsorption layer 250, a carbon-group material may be used, andalternatively, a polymer in which a black pigment or a black dye ismixed may be used.

FIGS. 7 and 8 illustrate optical absorption layers 260 and 280 includingmetal nanostructures.

Referring to FIG. 7, the spatial optical modulation device 205 includesthe first substrate 210, the optical absorption layer 260, and the phasetransition layer 220. The optical absorption layer 260 is formed bymixing metal nanostructures 262 of a spherical particle shape with ablack polymer 261. The black polymer 261 is formed of a polymer materialmixed with a black dye or pigment.

The structure of the spatial optical modulation device 205 asillustrated in FIG. 7 is such that the transfer of heat from the heatsource 120 is only in a vertical direction, i.e., a direction crossingthe optical absorption layer 260 and orienting to the phase transitionlayer 220, and the transfer of heat in a horizontal direction isminimized. According to this heat transfer pattern, heat may not bespread in the horizontal direction, thereby obtaining a relativelyminute pattern. As an example for implementing the minute pattern, thespatial optical modulation device 205 of the present embodiment employsthe optical absorption layer 260 in which the metal nanostructures 262having a good thermal conductivity are mixed with the black polymer 261.The diameter of each of the metal nanostructures 262 may be similar tothe thickness of the optical absorption layer 260, and accordingly, athermal conductivity of a thickness direction may be relatively higherthan a thermal conductivity of another direction.

Referring to FIG. 8, the spatial optical modulation device 207 includesthe first substrate 210, the optical absorption layer 280, and the phasetransition layer 220. The optical absorption layer 280 is formed bymixing metal nanostructures 282 of a nanorod or nanowire shape with ablack polymer 281.

The metal nanostructures 282 have a length that is the same as adistance between the first substrate 210 and the phase transition layer220, i.e., a length that is the same as the thickness of the opticalabsorption layer 280, and are arranged in a direction oriented away fromthe first substrate 210 and towards the phase transition layer 220.

As a method of forming the optical absorption layer 280 of the structuredescribed above, a method of forming vertical holes in the black polymer281 by etching or the like and filling a metallic material in thevertical holes may be used. Alternatively, a method of verticallygrowing the metal nanostructures 282 in a nanowire or nanorod shape andfilling a region between the metal nanostructures 282 with a material ofthe black polymer 281 may be used.

Since the optical absorption layer 280 having the structure describedabove transfers heat well only in a longitudinal direction of nanorods,i.e., a direction crossing the optical absorption layer 280, arelatively minute pattern may be formed on the phase transition layer220.

Referring to FIG. 9, the spatial optical modulation device 208 includesthe first substrate 210, the reflective layer 290, and the phasetransition layer 220. The reflective layer 290 is provided to increasethe efficiency of projecting, towards a viewer, a 3D image reproduced byinterference between the reproduction light Lr and a holographic patternP formed on the phase transition layer 220 when the reproduction lightLr is irradiated on the spatial optical modulation device 208. For thereflective layer 290, a metal thin film may be used.

Referring to FIG. 10, a spatial optical modulation device 209 includesthe first substrate 210, the optical absorption layer 250, thereflective layer 290, and the phase transition layer 220.

The spatial optical modulation device 209 of the present embodimentemploys both the optical absorption layer 250 and the reflective layer290 so as to prevent a writing beam irradiated by the heat source 120from arriving at a viewer and to transfer well to the viewer a 3D imagereproduced by interference between reproduction light and a holographicpattern.

Although the phase transition layer 220 in the spatial opticalmodulation devices 204, 205, 207, 208, and 209 of FIGS. 6 to 10 is shownin a thin film form without a pattern, the shown phase transition layer220 is only illustrative and may be modified to the phase transitionlayer 221 patterned onto a form having the plurality of regions 222 asshown in FIG. 3. In this case, the phase transition layer 220 may bemodified to a form having a vacuum-sealed space between the plurality ofregions 222 as shown in FIG. 4 or 5.

FIGS. 11A and 11B are block diagrams of an apparatus 600 for displayinga holographic 3D image, respectively showing a state in which phasetransition does not occur in a phase transition layer 420 and a state inwhich phase transition occurs in the phase transition layer 420 tothereby form a holographic pattern P on a liquid crystal layer 440,according to another exemplary embodiment.

The apparatus 600 according to the present embodiment differs from theapparatus 500 of FIGS. 1A and 1B in that a spatial optical modulationdevice 400 includes the phase transition layer 420 and the liquidcrystal layer 440 wherein the holographic pattern P generated by theholographic pattern generation unit 110 is optically addressed on theliquid crystal layer 440.

When phase transition occurs in a phase transition material forming thephase transition layer 420 due to heat applied by the heat source 120,an electrical characteristic of the phase transition material changes.That is, phase transition from a semiconductor to a metal, from aninsulator to a metal, or the like, causes a change in an electricalresistance. Due to the above electrical characteristics, an electricfield distribution in the liquid crystal layer 440 may be adjustedaccording to a phase transition phenomenon in the material. Since liquidcrystal molecules are aligned along a direction of an electric field, arefractive index distribution may be formed in the liquid crystal layer440 according to the electric field distribution to thereby form adesired holographic pattern.

In detail, the spatial optical modulation device 400 includes a firstsubstrate 410, a first electrode layer 430 formed on the first substrate410, the phase transition layer 420 formed on the first electrode layer430, the liquid crystal layer 440 formed on the phase transition layer420, a second electrode layer 450 formed on the liquid crystal layer440, and a second substrate 490 formed on the second electrode layer450. The first substrate 410 and the second substrate 490 are basemembers for forming the liquid crystal layer 9/10 by injecting andsealing liquid crystal molecules therebetween, and both or one of thefirst substrate 410 and the second substrate 490 may be omitted.

The first electrode layer 430 and the second electrode layer 450 areeach formed of a conductive material, and the second electrode layer 450may be formed of a transparent electrode material so that thereproduction light Lr emitted from the reproduction light source unit190 is transmitted to the liquid crystal layer 440. The first electrodelayer 430 may be formed of a metallic material or a transparentconductive material, and if the first electrode layer 430 is formed of ametallic material, the first electrode layer 430 may function as areflective layer as described with reference to FIG. 9.

The phase transition layer 420 is formed of a phase transition material,and the phase transition materials illustrated in the description of theapparatus 500 shown in FIGS. 1A and 1B,

According to the present embodiment, a phenomenon by which theelectrical property of the phase transition layer 420 changes inaccordance with phase transitions in the material is used, and atemperature distribution to be formed across the phase transition layer420 by the heat source 120 is determined in consideration of theholographic pattern P to be formed on the liquid crystal layer 440.

In detail, the liquid crystal molecules forming the liquid crystal layer440 are aligned along a direction of an electric field when the electricfield is formed in the liquid crystal layer 440 by a voltage appliedbetween the first electrode layer 430 and the second electrode layer450. The liquid crystal molecules have a property according to whichrefractive indexes thereof in a long-axis direction and a short-axisdirection are different from each other, and if a degree of alignment ofthe liquid crystal molecules varies according to a magnitude of theelectric field, a refractive index distribution in the liquid crystallayer 110 varies. That is, if local regions in the liquid crystal layer440 have electric fields different in magnitude than one another, arefractive index distribution in the liquid crystal layer 440 may beformed to thereby form a desired holographic pattern. According to thepresent embodiment, the electrical property, e.g., the property that anelectrical resistance varies, of the phase transition layer 420 is usedto form a refractive index distribution in the liquid crystal layer 440.Even though a constant voltage is applied between the first electrodelayer 430 and the second electrode layer 450, when a temperaturedistribution formed in the phase transition layer 420 by the heat source120 becomes equal to or greater than the phase transition temperature,an electrical resistance of a location where phase transition hasoccurred changes, and an electric field in a region of the liquidcrystal layer 440 corresponding to the location differs from an electricfield in the other region. As shown in FIG. 11B as an example, when acertain phase transition pattern P1 is formed on the phase transitionlayer 420, an alignment of liquid crystal molecules in a region of theliquid crystal layer 440 at a location corresponding to the phasetransition pattern P1 becomes distinguished from an alignment in theother region, and a holographic pattern P is formed on the liquidcrystal layer 440.

When the reproduction light source unit 190 irradiates the reproductionlight Lr onto the liquid crystal layer 440 on which the holographicpattern P is formed, a 3D image is reproduced.

The apparatus 600 according to the present embodiment may also display avideo in the method described with reference to FIG. 2. However, adetailed calculation and control of the heat source 120 performed by thecontrol unit 130 may differ from the embodiment of FIGS. 1A and 1B inthat, in the method described with reference to FIG. 2, a temperaturedistribution is determined in consideration of a change in an electricalproperty of the phase transition layer 420 so that a holographic patternP corresponding to a 3D image of a corresponding frame is formed on theliquid crystal layer 440.

FIG. 12 illustrates a spatial optical modulation device 401 which may beemployed in the apparatus 600 of FIG. 11, according to another exemplaryembodiment.

The spatial optical modulation device 401 differs from the spatialoptical modulation device 400 of FIGS. 11A and 11B in that the spatialoptical modulation device 401 includes a phase transition layer 421patterned onto a plurality of regions. The structure of the spatialoptical modulation device 401 as illustrated in FIG. 12 may form apattern having a relatively high resolution by reducing the transfer ofheat from local regions to adjacent regions when local regions of thephase transition layer 421 are heated as described with reference toFIG. 3.

The structures of the optical absorption layers 250, 260, and 280 andthe reflective layer 290 described with reference to FIGS. 6 to 10 maybe selectively or together employed in the structures of the spatialoptical modulation devices 400 and 401 employed in FIGS. 11A, 11B, and12.

As described above, according to the one or more of the above-describedexemplary embodiments, an apparatus and method for displaying aholographic 3D image may write and reproduce an inverse pattern ofvarious 3D images by employing a phase transition layer formed of amaterial of which phase transition occurs according to a temperature ina spatial optical modulation device and applying heat corresponding to ahologram pattern generated by a computer to the phase transition layer.

The phase transition material has a very short phase transition time andalso has a short time of returning from a transitioned phase to anoriginal phase, and thus, the apparatus for displaying a holographic 3Dimage may display a 3D video.

In addition, other exemplary embodiments can also be implemented throughcomputer-readable code/instructions in/on a medium, e.g., acomputer-readable medium, to control at least one processing element toimplement any of the above described exemplary embodiments. The mediumcan correspond to any non-transitory medium/media permitting the storageand/or transmission of the computer-readable code.

The computer-readable code can be recorded/transferred on a medium in avariety of ways, with examples of the medium including recording media,such as magnetic storage media (e.g., ROM, floppy disks, hard disks,etc.) and optical recording media (e.g., CD-ROMs, or DVDs). Thus, themedium may be a non-transitory medium according to one or more exemplaryembodiments. The media may also be used in conjunction with adistributed network, so that the computer-readable code isstored/transferred and executed in a distributed fashion. Furthermore,the processing element could include a processor or a computerprocessor, and processing elements may be distributed and/or included ina single device.

It should be understood that the exemplary embodiments described hereinshould be considered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould typically be considered as available for other similar featuresor aspects in other embodiments.

While one or more exemplary embodiments have been described withreference to the figures, it will be understood by those of ordinaryskill in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the presentinvention as defined by the following claims.

What is claimed is:
 1. An apparatus for displaying a holographicthree-dimensional image, the apparatus comprising: a holographic patterngeneration unit which generates holographic pattern information; aspatial optical modulation device comprising a phase transition layerformed of a phase transition material, wherein a phase of the phasetransition material changes according to a temperature thereof; a heatsource which applies heat to the phase transition layer; a control unitwhich controls the heat source according to the holographic patterninformation; and a reproduction light source which irradiates light ontothe spatial optical modulation device.
 2. The apparatus of claim 1,wherein the heat source is a laser light source.
 3. The apparatus ofclaim 1, wherein the phase transition material is a material thatundergoes a Mott transition.
 4. The apparatus of claim 3, wherein thephase transition material includes a material selected from a groupconsisting of vanadium dioxide (VO₂), vanadium trioxide (V₂O₃), europiumoxide (EuO), manganese oxide (MnO), cobalt oxide (CoO), cobalt dioxide(CoO₂), lithium cobalt dioxide (LiCoO₂), calcium ruthenium oxide(Ca₂RuO₄), strontium lawrencium oxide (SrLrO₄), and copper chloride(CuCl).
 5. The apparatus of claim 1, wherein the spatial opticalmodulation device further comprises a first substrate on which the phasetransition layer is formed, and wherein the phase transition layer ispatterned into a plurality of regions that are separated from one other.6. The apparatus of claim 5, wherein spaces between the plurality ofregions are vacuum-sealed.
 7. The apparatus of claim 6, furthercomprising: a second substrate formed on the phase transition layer, anda sealing member, wherein a space is formed around the plurality ofregions and defined by the first substrate, the second substrate, andthe sealing member, and wherein the space is vacuum sealed.
 8. Theapparatus of claim 5, further comprising a vacuum structure, wherein thefirst substrate is disposed in the vacuum structure.
 9. The apparatus ofclaim 5, further comprising an optical absorption layer formed betweenthe first substrate and the phase transition layer.
 10. The apparatus ofclaim 9, wherein the optical absorption layer comprises a black polymerand a plurality of metal nanostructures dispersed throughout the blackpolymer.
 11. The apparatus of claim 10, wherein each of the metalnanostructures has a spherical nanoparticle shape and a diameter of eachof the metal nanostructures is the same as a thickness of the opticalabsorption layer.
 12. The apparatus of claim 10, wherein each of themetal nanostructures has a nanorod or nanowire shape and a length ofeach of the metal nanostructures is equal to a distance between thefirst substrate and the phase transition layer, and each of the metalnanostructures extends between the first substrate and the phasetransition layer.
 13. The apparatus of claim 5, further comprising areflective layer formed between the first substrate and the phasetransition layer.
 14. The apparatus of claim 9, further comprising areflective layer formed between the optical absorption layer and thephase transition layer.
 15. The apparatus of claim 1, wherein thespatial optical modulation device further comprises a liquid crystallayer.
 16. The apparatus of claim 15, wherein the spatial opticalmodulation device comprises: a first substrate; a first electrode layerformed on the first substrate; the phase transition layer formed on thefirst electrode layer; a liquid crystal layer formed on the phasetransition layer; a second electrode layer formed on the liquid crystallayer; and a second substrate formed on the second electrode layer. 17.The apparatus of claim 15, wherein the phase transition layer ispatterned into a plurality of regions that are separated from one other.18. The apparatus of claim 1, further comprising a sensor configured tomeasure an ambient temperature of the phase transition layer.
 19. Theapparatus of claim 18, wherein the control unit stores therein a coolingcurve function of the phase transition material and adjusts an intensityof the heat source according to the ambient temperature measured by thesensor.
 20. A method of displaying a holographic three-dimensional (3D)image, the method comprising: applying heat to a spatial opticalmodulation device comprising a phase transition layer formed of a phasetransition material, according to holographic pattern information,thereby heating at least a portion of the phase transition layer to atemperature equal to a phase transition temperature or greater; andirradiating reproduction light onto the spatial optical modulationdevice.